Wednesday, 9 February 2011

IPT roll-out continues

We are continuing to roll out IP telephony to departments and one of the teaching hospitals will be set-up tomorrow (82 handsets).

We had to do a bit of prep work and change all the switches in the building over to Cisco 3750 POE switches to power the phones. Also setting up the voice VLANs to function across there and a few other 'fiddly' bits we discovered while setting up.

The 'fiddly' bits included the hospital emergency phone number being the start of a range of our numbers which caused a few head scratches, as well as the fact that, as the phones will be on the university network, they will be barred from calling the hospital number.

In the case of the emergency phone, the problem was that if the emergency number was 1111 and we had 5 digit extensions from 11110 through to 11119 then university personnel would be ringing the emergeny number by mistake.

To solve this we changed the Dial Plan to allow the four digit emergency number as an extension on our servers. Dialing this will point to a vector. This vector looks at the ANI (calling digits) and routes the call based on those. If the calling number is specified in a Vector Routing Table (which we put the new extensions in) then it will route to the Hospitals Control Centre DDI. If the ANI is not in the vector table then it will just play a message along the lines of 'This number is not valid' and hang up. Also, obviously, we had to reserve and not use the ten numbers in that range.

In the long term using IPT will not only provide many more features for the users but also make things easier for us. Every time someone moves their office around or swaps desks we will not have to go out to the building and re-patch from an EPN wiring frame, to a cabinet and to a socket. With their IP phones they can just plug in to any network socket and login and out of the phone as they wish.

The only existing wiring we will have to keep for now is the analogue lines for faxes and franking machines. But these do not move around so much.

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